A wide range of medical procedures involve placing objects, such as sensors, tubes, catheters, dispensing devices, and implants, within the body. Real-time imaging methods are often used to assist doctors in visualizing the object and its surroundings during these procedures. Some methods track the objects using the object using magnetic fields. However, disturbances in the magnetic field may create errors in the tracking.
U.S. Pat. No. 6,714,008, to Holmes, et al., whose disclosure is incorporated herein by reference, describes a gradiometric measurement methodology for determining magnetic fields of large objects.
U.S. Patent Application 2004/0034515, to Bar Tal, et al., whose disclosure is incorporated herein by reference, describes a method for estimating position and orientation measurements in electromagnetic systems. The method includes minimizing the difference between a model for the measurements and one or more measurements.
W.I.P.O Patent Publication WO/2004/006770, to Sati, et al., whose disclosure is incorporated herein by reference, describes a method for calibrating medical imaging systems. The method is stated to be able to determine a position of an imaging source and, if applicable, a magnetic field distortion, for each of a plurality of orientations of a C-arm imaging device.
U.S. Patent Application 2005/0107687, to Anderson, whose disclosure is incorporated herein by reference, describes a system for distortion reduction in an electromagnetic tracker. Certain embodiments of the system are stated to include a tracking analysis unit for analyzing a tracking behavior of an instrument and a tracking modification unit for compensating for the tracking behavior of the instrument.
U.S. Patent Application 2007/0055125, to Anderson et al., whose disclosure is incorporated herein by reference, describes an electromagnetic tracking system that includes a field generator and a field sensor arranged to generate and detect, respectively, an electromagnetic field.
U.S. Patent Application 2008/0183064, to Chandonnet et al., whose disclosure is incorporated herein by reference, describes a method for detecting electromagnetic (EM) field distortion. The method includes sampling a sensor assembly positioned within a volume of interest to acquire measurements of EM fields within the volume of interest, and monitoring the measurements to detect EM field distortion within the volume of interest.
U.S. Pat. No. 6,147,480, to Osadchy et al., whose disclosure is incorporated herein by reference, describes a method for tracking an object using energy fields, in the presence of interference due to introduction of an article responsive to the fields, and in the vicinity of the object.
U.S. Pat. No. 5,767,669, to Hansen et al., whose disclosure is incorporated herein by reference, describes a system for determining the position and orientation of remote sensors using pulsed magnetic fields generated from a fixed location. Eddy current distortions are sensed separately and subtracted by the system.
U.S. Pat. No. 7,657,075, to Viswanathan, whose disclosure is incorporated herein by reference, describes a method for determining a transformation of a three-dimensional pre-operative image data set to obtain a registration of the three-dimensional image data with an X-ray imaging system.
U.S. Pat. No. 7,689,019, to Boese et al., whose disclosure is incorporated herein by reference, describes a method and a device for registering 2D projection images of an object relative to a 3D image data record of the same object. A 3D feature contained in an object, which is also identifiable in the 3D images, is symbolically reconstructed.
U.S. Patent Application 2009/0010540, to Mullick et al., whose disclosure is incorporated herein by reference, describes a method for performing image registration. The method comprises obtaining a reference image dataset and a target image dataset and defining an image mask for a region of interest in the reference image dataset.
U.S. Patent Application 2002/0172328, to Dekel, whose disclosure is incorporated herein by reference, describes a method for transforming the spatial coordinates of an instrument into its corresponding X-ray projection image. The method is stated to be based on the registration of the coordinates system of an X-ray beam imaging system with a location device by simultaneously recording the spatial coordinates and the X-ray projection images of a calibration tool.